Nextbigfuture described how 200 large space stations could be built by 2040 to hold 2 million people. There are videos that provide more details on the SpaceX BFR and the Kalpana space station.
Below are two intermediate space stations that would be stepping stones leading to serial production of Kalpana space stations.
Resupply and temporary construction space station using Bigelow modules
This may not be needed and may not be the most affordable option because leaving six to eight Big Falcon Spaceships in orbit would probably cost less and provide similar habitable volume.
This is a reasonably sized existing proposal for use while the larger Kalpana stations are built. Bigelow modules or Big Falcon Spaceships that are linked for rotation
Resupply Depot Hercules (8300 m3) – Six BA 330 modules, three BA 2100 modules, nine propulsion buses with docking node and three crew capsules.
PB/DN: Combination of a Propulsion Bus attached to a Docking Node, weighs 17 mT
PB/DN Stack: Three PB/DNs attached to a Falcon Heavy that is on the Launch Pad
BA-330 Module: A Bigelow space station module that has a pressurized volume of 330 cubic meters, weighs 25 mT, and can hold 6 crew
BA-300 Stack: Two BA-300s attached to a Falcon Heavy that is on the Launch Pad
BA-2100 Module: A Bigelow space station module that has a pressurized volume of 2,100 cubic meters, weighs 100 mT, and can hold 16 crew
Hercules Space Station
(3) BA-2100 Modules
(6) BA-330 Modules
Hercules Space Station Weight
Three (3) BA-2100s = 3 * 100 mT = 300 mT
Six (6) BA-330s = 6 * 25 mT = 150 mT
Three (3) PB/DNs = 3 * 17 mT = 51 mT
Therefore, the space station weighs 501 mT.
Hercules Space Station Crew Size
Three (3) BA-2100s = 3 * 16 Crew = 48 Crew
Six (6) BA-330s = 6 * 6 Crew = 36 Crew
Therefore, the space station has a crew of 84.
Hercules Space Station Pressurized Volume
Three (3) BA-2100s = 3 * 2100 m^3 = 6,300 m^3
Six (6) BA-330s = 6 * 330 m^3 = 1,980 m^3
Therefore, the space station has a pressurized volume of 8,280 m^3.
This also comes out to 99 m^3 per crew member.
Hercules Space Station Launching
Three (3) BA-2100s @ 1 SLS-IA per BA-2100 = 3 BA-2100 Stacks
Six (6) BA-330s @ 1 Falcon Heavy per two (2) BA-330s = 3 BA-330 Stacks
Three (3) PB/DNs @ 1 Falcon Heavy per three (3) PB/DNs = 1 PB/DN Stack
Hercules Space Station Cost Estimate
Three (3) BA-2100s = 3 * $500,000,000 = $1,500,000,000
Six (6) BA-330s = 6 * $125,000,000 = $750,000,000
Three (3) PB/DNs = 3 * $75,000,000 = $225,000,000
Four (4) Falcon BFR = 4 * $25,000,000 = $100,000,000
The space station has a total cost of $2,575,000,000 (USD).
A ten thousand person colonization spaceship design was proposed by Icarus Interstellar with a focus on how the community and living spaces should be designed. People are assigned area with the density of the city of Seattle and standard mixed-use living areas. Everyone has 50 square meters of living space. There is agricultural and other green areas.
Without propulsion it could be used as an initial large-scale space station with rotation for gravity. It could be placed in equatorial low earth orbit (ELEO) for low radiation.
40 BA-2100 modules or Big Falcon Spaceships would be $10 to $20 billion. SpaceX BFR might be able to launch two BA-2100 modules at a time.